Use the SuperLooper Loopback Jack & Plug together with your Gigabit Ethernet switch or hub to check for breaks or shorts in your network wiring. When plugged into a wall jack or onto a network cable, the loopback completes a circuit to your switch or hub. If the connection LED on your switch or hub lights up, your cable is OK. Please note, however, not all Gigabit Ethernet systems support loopback operation. Since Gigabit Ethernet requires all four network cable pairs, loopback read as crosstalk. For the SuperLooper to work, a compatible system needs to switch down to 10/100 mode.